A rare disease, also known as an orphan disease, is a medical condition that affects a small percentage of the population. In most countries, a disease is considered rare when it affects fewer than 1 in 2,000 people. These diseases often pose significant challenges in developing treatments due to the limited number of patients available for clinical trials and research. Consequently, the costs of research and development for treatments can be disproportionately high compared to more common diseases. This combination of limited patient population and high research and development costs makes it difficult for pharmaceutical companies to invest in developing treatments for rare diseases.